In this work, the effect of low concentration of Barium (Ba) on the density, crystal structure, microstructure and dielectric properties of K0.5Na0.5NbO3 (KNN) lead-free piezoelectric ceramic samples have been systematically studied. The samples were calcined at 850 °C for 6 hours and pressed using a hydraulic hand press to produce a green body disc. In this way, the green body disc of KNN was doped with 0.00 to 0.10 mol % of Ba concentration and was placed in an alumina crucible before conventional sintering at 1120 °C for 2h in air atmosphere. The increasing amount of Ba shifting all the diffraction peaks to a higher angle was measured using X-Ray Diffraction. Doping the Ba also improved the density of the KNN body. The most densified body was identified for x= 0.05 mol% of Ba which is 4.21355 g/cm3. The microstructure of the surface becomes finer and smaller after Ba doping. This shifting diffraction peaks and densified body is responsible for the enhancement of dielectric properties with the optimum value obtained from the sample doped with x= 0.05 mol%. The results show that relative permittivity (ɛr) was improved by the increment of Ba2+ concentration for 0.05 mol% which is 183.9856 for 1 kHz.
CaCu3Ti4O12 (CCTO) is an electroceramic material with complex cubic perovskite-like oxide. It possessed a giant dielectric constant of about 105 over a wide temperature range (100-600 K). In this work, CCTO was synthesized through solid state method. The effect of different heating rate during sintering process was studied. The raw materials - CaCO3, CuO and TiO2 were wet ball milled for 24 hours and calcined at 900 °C for 10 hours. Then the calcined powder was pressed into pellet shape at 300 MPa. Sintering was done at 1040 °C for 12 hours with different heating rates: 3, 5 and 10 °C/min. The phase formation and surface morphology was investigated by X-Ray Diffraction (XRD) and Field Emission Scanning Electron Microscope (FESEM), respectively. The density was measured by Archimedes Principle. XRD pattern proves the CCTO single phase formation for the calcined powder and sintered pellet. The SEM images show the different grain size for different heating rate. The density of the pellet was found to be reduced when faster sintering heating rate was used.
The effect of ZnO-B2O3-SiO2 (ZBS) glass additives to the microstructure and electrical properties of CaCu3Ti4Oi2 (CCTO) electroceramic has been successfully investigated in this research. CCTO and ZBS glass additives were prepared via solid state reaction and melt quench techniques, respectively. Raw materials of both CCTO and ZBS were wet mixed separately for 24 hours, dried overnight and the CCTO powder was calcined at 900 °C for 12 hours using an electrical carbolite furnace. After that, the ZBS powder was melted at 1400 °C for 2 hours using an elevator hearth furnace. The ZBS glass was grinded to form fine powder. Different weight percentages (0, 1, 3, 5, 7 and 10 wt%) of ZBS glass powder were added into CCTO (CCTO-ZBS powders), then the powders were wet mixed for 24 hours. The CCTO-ZBS mixtures were dried overnight, compacted at 300 MPa using hydraulic pressure of 6 to 9 mm diameter and 1 to 2 mm thickness (for dielectric properties test) and at 200 MPa of 50 mm diameter and 3 mm thickness (for dielectric breakdown strength test), then sintered at 1040 °C for 10 hours using an electrical carbolite furnace. The addition of a small amount of ZBS glass about 1 wt% was able to increase the dielectric constants (33.99%) and reduce the dielectric loss (5.14%) of CCTO measured at 1 MHz. This addition has also increased the relative density to the maximum value (95.90%), helped the formation of single phase of CCTO, increased the grain size (0.35%) and reduced the porosity as compared to pure CCTO. Meanwhile the dielectric breakdown strength (58.0%) and volumetric energy storage density (80.9%) has also improved with 7 wt% of ZBS glass addition.
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